Binder-free compact zeolite preforms and method for the production thereof

ABSTRACT

The present invention relates to compact zeolite preforms, which are characterized in that they have as high a zeolite content as possible determined by means of suitable adsorption methods. A further aspect of the present invention relates to a method for producing compact zeolite preforms, said method being characterized in that: a) a mouldable mixture, comprising zeolite, one or more zeolite precursor components, water (if necessary) and one or more organic additives (if necessary) is processed into preforms; b) the preforms obtained in this way are subjected to thermal treatment; and c) the thermally treated preforms are watered, aged and brought into contact with a further component from which, in combination with the zeolite precursor components, zeolite can be produced and exposed to conditions under which zeolite forms from the further component and the zeolite precursor components. Preforms which can be produced according to this method can advantageously be used for adsorption processes or thermal-chemical applications, for example in energy storage, or as a catalyst, or a component in a catalyst or as a supporting material for zeolite membranes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase of PCT Application NumberPCT/EP2013/070957 filed Oct. 8, 2013 which claims priority to Germanpatent application DE102012020217.2 filed October 15, the entirecontents of which are hereby incorporated by reference herein.

BACKGROUND

Zeolites belong to the class of crystalline aluminosilicates to theclass and were originally discovered as a natural mineral. Thecomposition of the substance group of zeolites can be described by thefollowing formula (I):

M_(n)O.Al₂O₃ .xSiO₂ .yH₂O  (I)

wherein the factor n indirectly determines the charge of cation M, whichis typically present as an alkali or alkaline earth metal cation. Thefactor y indicates how many water molecules are present in the crystal.The molar ratio of SiO₂ to Al₂O₃ in the empirical formula is referred toas modulus (x)¹.

SUMMARY

Commercial interests have mainly obtained synthetic zeolites with afaujasite structure in which two types can be distinguished, dependingon their chemical composition. Products with a corresponding frameworkstructure and a modulus of >2, but under 3.0 are referred to asX-zeolites, whereas those with a modulus >3 are referred to asY-zeolites. Other important zeolites are those with a Linde type Astructure. These have a chemical composition matching the zeoliteframework, which is characterised by a modulus of 2.

Through the freely selectable cations, the pore size and poreaccessibility of the zeolite framework can be influenced and the polarproperties of the zeolite type can be changed.

Due to their high chemical and thermal stability, the presence of aregular pore system with pore openings in the sub-nanometre range andthe ability to form specific interactions with adsorbed molecules (due,among other things, to a variable cation composition) zeolites are idealadsorption agents and in a tried and tested way are used both in static,i.e. non-regenerative adsorption processes (for example, the drying ofintermediate pane volumes in insulated glass windows²) as well as indynamic, i.e. regenerative adsorption processes (drying and purificationof gases and liquids as well as the separation of substances²). Sincethe process of adsorption proceeds with the release of heat, the processof regeneration however (desorption) proceeds with heat absorption: Itis also possible to use zeolites for heat storage and transition, thuscontributing to the conservation of the environment³. After any periodof time, the quantity of heat absorbed in the desorption process canpractically be released again, almost in full as adsorption heat⁴⁵. Withappropriate technology, the described effect can also be used forrefrigeration⁶. Furthermore, zeolites are used as a catalyst⁷, catalystcomponent⁸ or a component for zeolite membranes⁹.

As a rule, since a fluid medium must flow around the adsorption activecomponent in dynamic (regenerative) applications, the correspondingprocess technique uses so-called absorbers filled with a bed consistingof adsorbent agents. Here, in order to avoid excessive pressure lossesacross this bulk material, the use of zeolite preforms of a certainminimum size is generally desirable.

The known method for gas or fluid processing¹⁰ that is already used inpractice (as well as for catalysis¹¹, heat storage¹² and heattransition) works with a bed that mostly consists of very small bodies,such as zeolite spheroid granules or strands. The volumetric adsorptioncapacity of such a zeolite bed depends on its bulk density, and this inturn, with equal materials, depends on the filling of space/packingdensity: The maximum filling of space for spheres with a uniform size is74% (packed as dense as possible). In order to increase theeffectiveness of the relevant processes, greater space filling (moreactive material per volume) may be desirable. This can theoretically beachieved through the use of mixtures consisting of perfectly matchedsphere sizes. However, such optimized mixtures are very expensive toproduce and apart from this, higher filling of space usually leads to anundesirable increase in pressure loss (worse flow-through) in thecorresponding bed. A honeycomb body represents an alternative. Even at aratio of 1 (cell connector width to channel diameter) over 80% of spacecan be filled with hexagonal and triangular honeycomb geometries (Table1). From a geometrical consideration, at a 3 to 1 ratio of cellconnector width to channel diameter, all geometries achieve a spacefilling index of approx. 95%. At the same time, flow travels throughhoneycomb bodies easily. As a result of the mutual locking of honeycombchannels, it is possible to create a forced flow through the cellconnectors and thus, a further increase in efficiency. By subsequentlyapplying a densely crystallised layer of zeolites, these compact zeolitepreforms can also be used for separation on the basis of size orselective adsorption (membrane separation).

TABLE 1 Space filling for a bed of spheres and different honeycombgeometries. Channel Cell connector Space filling Geometry size widthindex Sphere packing — — 74% Multi channel tube (round) 1 1 72% Squarehoneycomb 1 1 75% Hexagonal honeycomb 1 1 82% Triangular honeycomb 1 185% Multi channel tube (round) 0.5 1.5 93% Square honeycomb 0.5 1.5 94%Hexagonal honeycomb 0.5 1.5 95% Triangular honeycomb 0.5 1.5 96%

In addition, the adsorption capacity of zeolite beds and/or zeolitesolid bodies depends on the amount of the adsorption-active zeolitesubstance.

As zeolite powder (products of classical zeolite synthesis) does notexhibit any binding capacity, adsorption-inert binders are used inpractice to produce the corresponding compact preforms^(13,14) orgranules¹⁵. The introduction of the binder (as mentioned) causes a‘dilution’ of the active component and as such, this leads to loweradsorption capacities. Furthermore, the use of an adsorption-inertbinder, at least without the use of additional additives as poreformers, leads to the impairment of the actually desired adsorption anddesorption processes on the pure zeolite component. This is becauseoften, compression takes place in the process of shaping throughstructure granulation, extrusion, etc. and at the same time, a poretransportation system is formed which may be unfavourable for theapplication¹⁵. However, in most cases binder containing zeolite preformshave to be highly porous in order to prevent the mobility of theadsorbing and desorbing molecules as little as possible. Highly porouspreforms are obtained for example, by mixing pore formers to thezeolite-binder mixture before the shaping of zeolite preforms containingbinder. The added pore formers are burnt out in the final thermalactivation of the preform and in doing so, leave a corresponding poresystem^(16,17). There is also the possibility to use water-soluble poreformers¹⁸.

A further possibility of producing zeolite-containing compact preformsis so-called ‘washcoating’. In this case, adsorptive-active and/orcatalytically-active powder is applied onto an inert or low active,compact base body (for example honeycomb) as an outer zeolite layer,this also takes place using a non-zeolite binder^(19,20).

In recent publications, the crystallization of, for example, zeoliteZSM-5 has been described, directly on an aluminium foam²¹. However, thismethod is relatively complex and gives only provides relatively thinzeolite layers on the aluminium cell connectors.

An improvement to the effect of zeolite beds in the adsorption processescould be achieved by the introduction of so-called binder-free zeolitesphere granules or strands^(18, 22-26). By forming the very distinctpore transportation system in the granules, the disadvantages of thebeds of binder-containing spheroid granules are considerably reduced²⁴.They are characterized by a smallest possible proportion of mesopores (2nm to 50 nm)²⁷, but as many macropores as possible (>50 nm). Theequilibrium adsorption capacities match those of a zeolite powder withan identical chemical composition¹⁵.

The prior art describes classically produced compact preforms based onbinders whose binder content leads to a considerable reduction in theadsorptive and/or catalytically active proportion. Through extrusion,these can be produced from a mixture consisting of zeolite, a mixture oftwin-layered and triple-layered clay minerals, inorganic fibre materials(e.g. fibreglass²⁸, zirconium dioxide²⁹) and glucans³²⁸. In suchproducts, the equilibrium adsorption capacity is reduced by the amountof adsorption-inert binder used. In addition, the apparent insufficientporosity of the pore transportation system is indicated by the very slowwater absorption.

Siloxane compounds are also described as suitable binders for theproduction of zeolite 3A, 4A, 5A or X-honeycombs³⁰. Apart from the factthat the adsorption-inert binder is also produced from siloxanecompounds during processing, the solvent contained in siloxanederivatives (albeit in a small quantity, which can only be removed byapplying solvent-specific safety rules) is considered as a disadvantageof this method. The low activation temperature of 280° C. (max.) furtherdescribed in this method, indicates a power-saving activation process.However, at these temperatures, the required activation state of thefinished preform may, if at all, only be achieved within very longactivation times. In the present work, ‘activation’ describes a thermaltreatment of the zeolite material, wherein the zeolite is displaced inan activation state that is required for the application of the compactzeolite preforms, i.e. one that retains negligible residual moisturecontent for the application.

The use of pore formers is described in order to improve the poretransportation structure in the production of compact, binder-containingzeolite preforms preforms³¹. A disadvantage here, are the hightemperatures required to remove the pore former and solidify the binder(up to 850° C.). In this case, the adsorption capacity is also reducedthrough the proportion of adsorption-inert binder.

Taking the prior art described above into account, there is therefore ademand for compact zeolite preforms, which do not have the disadvantagesof the prior art. In particular, a need exists for compact zeolitepreforms which contain no additional binders or solidifier materials andthus contain a very high proportion of zeolite in a defined volume.

Furthermore, there is need for a technical method which is as efficientas possible and which allows for the inexpensive production ofmechanically stable, compact zeolite preforms. The compact zeolitepreforms that are produced should preferably have a maximum level ofactive zeolite material, e.g. in the form of zeolites with a faujasitestructure (comprising both zeolite X as well as zeolite Y) or the Lindetype A structure.

In the present invention, products and methods are described, whichsatisfy the aforementioned and generally do not have the disadvantagesof the prior art.

The present invention relates to compact zeolite preforms, which arecharacterized in that they have a zeolite content of at least 90%,defined by means of suitable adsorption methods, and preferably at least95%. Furthermore, the present invention relates to a method forproducing compact zeolite preforms, which is characterised in that a) amouldable mixture, comprising zeolite, one or more zeolite precursorcomponents, water (as necessary) and one or more organic additives (asnecessary) is processed into preforms; b) the preforms obtained in thisway are subjected to thermal treatment; and c) the thermally treatedpreforms are watered, aged and brought into contact with a furthercomponent from which, in combination with the zeolite precursorcomponents, zeolite can be produced and exposed to conditions underwhich zeolite forms from the further component and the zeolite precursorcomponents. Another aspect of the present invention relates to compactzeolite preforms which can be produced according to such a method, aswell as the use of such compact zeolite preforms for adsorptionprocesses or thermal-chemical applications, e.g. in the storing ofenergy, as a catalyst, or component of a catalyst or as a supportingmaterial for zeolite membranes. The compact zeolite preforms arecharacterised by high adsorption capacities that are not affected by anadsorptive inert binder additionally contained in a zeolite preform orother adsorptive inert materials.

When the term ‘water absorption capacity’ is used in the following text,it refers to the specific equilibrium adsorption capacity for water onmaterials that have been thermally treated at 450° C. over a period oftwo hours at a temperature of 20° C. and a relative humidity of 55%.

A first aspect of the present invention relates to compact zeolitepreforms which are characterized in that they have a zeolite content ofat least 90% and preferably at least 95% by means of suitable adsorptionmethods. For establishing the zeolite content determined in this way,the water adsorption capacities the compact zeolite preforms related tothe invention and the initial zeolite powder of the same zeolitestructure and same chemical composition were used in proportion to eachother. The compact zeolite preforms in accordance with the invention arepreferably based on zeolite Y, preferably with a modulus greater than4.9, and more preferably in the range of 4.9 to 5.5, zeolite X orzeolite A or a mixture of zeolite types.

A compact zeolite preforms, as this term is used in connection with thepresent invention, is a preform which preferably has a space fillingindex of 80% or more, particularly preferably 85% or more, and mostpreferably 90% or more. Within the scope of the present invention, nopreform is a preform from which conventional adsorption agents orcatalyst beds can be generated (e.g. in the form of spheres or shortextruded (as the case may be, hollow) strand preforms). Even spheroidgranules that have sizes of sphere that are perfectly matched (asdescribed above) do not fall within the definition of a compact zeolitepreform. It is crucial that the compact zeolite preform is used as such,and not in the form of a bed of a variety of bodies, which takentogether have the characteristics of a bed.

With regard to the shape, the compact zeolite preform according to thepresent invention are not subject to any relevant restrictions. Thecompact zeolite preforms in accordance with the invention can, forexample, take the form of a plate, a tube, a solid cylinder or ahoneycomb. However, it is preferable that they have a high a spacefilling index as possible and, at the same time comparatively very goodthrough flow characteristics, for example, as is found in a honeycombshape with a broad cell connectors and narrow channels.

For the compact zeolite preforms in accordance with this invention, itis preferred that they are substantially free of non-zeolite components.

In the context of the present invention, zeolites with a faujasite orLinde type A structure (or mixtures of both types of zeolites and/ortheir use in the method described in the following section) arepreferred.

If they been produced on the basis of a zeolite with a Linde type Astructure, the compact zeolite preforms in accordance with the inventionpreferably have a water absorption capacity of at least 22 wt. %, andmore preferably, at least 24 wt. %. If they have been produced from azeolite X, they may have a water absorption capacity of at least 27 wt.%. Particularly preferably they have a water absorption capacity of atleast 29 wt. % and most preferably they have a water absorption capacityof at least 30 wt. %. If, on the other hand, they have been produced onthe basis of zeolite Y, they may have a water absorption capacity of atleast 27 wt. %. Particularly preferably they have a water absorptioncapacity of at least 28 wt. % and most preferably they have a waterabsorption capacity of at least 29 wt. %.

Another aspect of the present invention relates to a method forproducing compact of zeolite preforms, characterized in that a) amouldable mixture, comprising zeolite, one or more zeolite precursorcomponents, water (as necessary) and one or more organic additives (asnecessary) is processed into preforms; b) the preforms obtained in thisway are subjected to a thermal treatment; and c) the thermally treatedpreforms are watered, aged and brought into contact with a furthercomponent from which, in combination with the zeolite precursorcomponents, zeolite can be produced and exposed to conditions underwhich zeolite forms from the further component and the zeolite precursorcomponents.

In this method powdered zeolite is preferably used as a raw materialwhich, as a consequence of its structural composition, is notplasticizable in its pure form is and thus does not represent apreferable raw material for plastic forming processes. This zeolite ismixed with one or more zeolite precursor components. The main is zeoliteprecursor components are preferably clay minerals with the chemicalcomposition Al₂Si₂H₄0₉ such as kaolinite or halloysite. Other zeoliteprecursor components can be, for example, sodium hydroxide or sodiumsilicate. As the zeolite precursor components are supposed to beconverted to zeolite in the novel process, they may essentially consistof chemical elements/compounds contained in the corresponding zeolite.

According to the prior art, it is very difficult to use kaolincontaining kaolinite as a main component as a binder e.g. for themixtures intended for the extrusion. This is because, under certaincircumstances, these mixtures are much more difficult to plasticize thanother systems.

In order to improve the plasticity of the mass to be deformed, waterand/or an organic components (with a temporary binder effect and/orlubricant) can be added in appropriate amounts as additives initialmixture consisting of zeolite and zeolite precursor components.

Within the context of step a), the resulting mass is then processed byan appropriate method to form preforms i.e. formed into the desiredshape. Extrusion, pressing or casting can be used as a preferablemethod.

In a particularly preferred embodiment, preforms are processed throughextrusion. In the extrusion process the known units from the prior beused. The plastic mixture produced in a twin shaft mixer is preferablyextruded with a vacuum screw extruder to form continuous strands,wherein the strands are subsequently shortened to form a manageablelength and are then preferably dried with 5 to 20% loss on drying, orparticularly preferably, with 5 to 10% loss on drying. Loss on dryingrefers to the quantity of water which the tested sample loses within anhour when treated at 105° C.

In a further particularly preferred embodiment, preforms are processedby pressing a mixture of zeolite, zeolite precursor components and/orwater and/or one or more organic additives, preferably a polyvinylalcohol solution.

When processed by pressing, it is also preferable that granules areinitially produced from a kaolin-zeolite-mixture, preferably by means ofa thermal granulation process in accordance with the prior art, and morepreferably by means of a mechanical granulation process in accordancewith the prior art by adding a solution consisting of one or moreorganic components having temporary binder effect. This may take placein a mixer which contains the kaolin-zeolite mixture. Afterhomogenising, the granules obtained in this way are dried and pressed ona dry press to form preforms.

In a another particularly preferred embodiment, the processing to formpreforms is carried out by casting a zeolite-kaolin-water mixture (asnecessary, with the addition of further components) into a dry gypsummould.

When processing by casting, it is preferable that the kaolin-zeolitemixture is processed with deionized water and a dispersant (preferablybi-functional Carboxylic acids) in a grinding drum with the aid ofgrinding balls to form a homogeneous, pourable slurry. The slurryproduced in this way is poured into a porous mould. The mould removesthe water from the zeolite-kaolin-water mixture resulting in a so-calledshard which is removed from this mould after an appropriate holding timeand then dried.

In a method according to the invention, a type 4A or X or Y driedzeolite powder is preferably used as an initial material. Thispreferably uses a modulus greater than 4.9, and more preferably in therange of greater than 4.9 to 5.5. The zeolite powder that is describedcan be used as a filter cake or as a slurry, wherein the correspondingmoisture content must be taken into account in the processing of themass to be deformed.

It may be desirable that the main zeolite precursor components do notexceed a proportion of non-convertible zeolite components, e.g. 5 wt. %mica or quartz, and preferably 1 wt. %.

In the mouldable mixture in step a) of the described process, thezeolite and the zeolite precursor components are preferably used in aweight ratio of 10:1 to 1:10, more preferably 1:1 to 6:1. If necessary,an additional organic components with a temporary binder effect and/orlubricants and/or water may be incorporated into the mixture.

In step b) of the process described above, the preforms obtained fromstep a) are subjected to thermal treatment. In so doing, it is preferredif the preforms are heated to a temperature of 550° C. to 850° C.,preferably 550° C. to 650° C. For this thermal treatment, it may beadvantageous if the preforms are initially dried before the thermaltreatment, preferably at a dry loss of 5-10%. During the thermaltreatment, the organic component that may remain is removed, the zeoliteprecursor components are subjected to a structural conversion and themain casting is solidified. Subsequently, the resulting preforms arecooled down, free of cracks.

At this point in the technology chain, the preforms can, if necessary,be cut to the desired shape.

Before the heat-treated preforms are brought into contact with anothercomponent, they are preferably subjected a wash in step c). For this,the heat-treated preforms are treated with water or a diluted sodiumhydroxide solution (a NaOH solution between 0.5% and 5%, preferablybetween 1% and 2%).

In the case of the further component which is likewise brought intocontact with the thermally treated preforms during step c), these is acomponent which, as necessary, in terms of its nature or quantity,contains chemical elements or compounds that lack the zeolite precursorcomponents compared to the zeolite to be produced in step c).Preferably, the further component is an alkali silicate solution oralkali aluminate solution, and more preferably a sodium silicatesolution or a sodium aluminate solution. It is further preferable that,an alkali silicate solution is used as an additional component if, inthe course of step c) zeolite is to be formed with a faujasitestructure. In the case of the intended production of zeolite with aLinde type A structure in step c), it is preferable if an alkali metalaluminate solution is used as a further component.

The heat-treated preform is preferably brought into contact with thefurther component in step c) at a temperature ranging from 75° C. to100° C. and particularly preferably, at a temperature ranging from 80°C. to 95° C. In this step, it is further preferable that the additionalcomponent is brought into contact with the zeolite precursor componentsover a period of 1 to 48 hours, and preferably 8 to 24 hours. In aparticularly preferred embodiment, in addition to the temperaturetreatment described above, the process of bringing the further componentinto contact with the zeolite precursor components comprises aging thatthat takes place prior to this temperature treatment. This takes placeat a temperature of 15° C. to 60° C., preferably 20° C. to 35° C., overa period of 0.5 h to 24 h, preferably 1 h to 5 h. It may be irrelevantwhether a solution of the other component is used for the aging and heattreatment, or whether an initial solution of the other component is usedfor the aging while a second solution is used for the temperaturetreatment. With regard to its composition, the second solution may bethe same or different from the initial solution.

Furthermore after washing is carried out (as necessary) and/or aging iscarried out (as necessary) and the treatment is carried out at 80° C. to95° C., it is preferable if the product obtained from the methoddescribed in the previous sections is brought into contact with one ormore washing solutions. These washing solutions are preferably water,more preferably deionized water and/or sodium hydroxide solutions, thelatter being preferably at a concentration of 0.01 to 10%, and mostpreferably at a concentration of 0.5 to 5%. After washing with thewashing solution, the product can additionally be washed with water,preferably deionized water, then dried and subsequently activated.

In a particularly preferred embodiment, the compact zeolite preforms inaccordance with the invention are treated as follows within the scope ofstep c):

The compact preforms obtained in step b), are first subjected to a“wash”. For this, rinse water or a diluted sodium hydroxide solution(the solution contains between 0.5% and 5%, preferably between 1 and 2%NaOH) continuously flows through the material in an agitator vessel orin a column filled with compact preforms. The weight ratio ofdemineralized water or sodium hydroxide to compact (rough) preforms is5:1 to 50:1, and preferably between 8:1 and 18:1. The washing is carriedout at a temperature between 15° C. and 40° C., and preferably at roomtemperature. The washing process is completed within 3 mins. to 120mins, and preferably 15 mins to 60 mins. The compact, washed preformsare preferably aged in an aqueous reaction consisting of sodium silicateand sodium hydroxide in the case of the conversion of non-zeolitematerial into a zeolite with a faujasite structure and an aqueousreaction consisting of sodium aluminate and sodium hydroxide in the caseof the conversion of non-zeolite components into a zeolite with a Lindetype A structure, i.e. the material is left in the respective solutionat 15° C. to 60° C., preferably between 20° C. and 35° C. for 0.5 h to24 h, preferably 0.5 h to 5 h. The subsequent conversion of thenon-zeolite components into zeolite can be carried out in a suitablevessel, preferably an agitator vessel or (additionally flowed through ina continuous concentration that was similar to the reaction solution orthe same solution as was used for aging) using the column filled withcompact preforms. At the same time, the weight ratio of the reactionsolution to the compact preforms is between 5:1 to 50:1, and preferably8:1 to 18:1. The reaction temperature should be selected between 75° C.and 100° C., and preferably between 80° C. and 95° C. The time untilreaching compact preforms consisting entirely of zeolite is between 8 hand 48 h. After the end of the reaction time, the compact zeolitepreforms are washed with deionized water for so long, until the pH valueis below 12. As a result of a preliminary washing step with a dilutedsolution of sodium hydroxide with a concentration of between 0.01% and10%, and preferably between 0.5 and 5% NaOH, the amount of washing watercan be reduced.

The spent reaction solution from the conversion step can be recycled andused again for a subsequent treatment step with new compact preforms.

A further aspect of the present invention relates to compact preformsconsisting entirely of zeolite, known as compact zeolite preforms in thefollowing, which are obtainable in accordance with a method as describedabove. These compact zeolite preforms preferably have a zeolite contentof at least 90% and preferably at least 95%, as determined by means ofsuitable adsorption methods.

The compact zeolite preforms according to the invention are preferablymade of zeolite Y, preferably with a modulus greater than 4.9, and morepreferably, in a range greater than 4.9 to 5.5, or zeolite X or zeoliteA.

The compact zeolite preforms produced by this method can for example,take the form of a honeycomb structure, a single or multi-channel tube,a plate, or a solid cylinder.

Surprisingly, in connection with the extrusion, the technology chaindescribed above starting from zeolite and zeolite precursor components(which do not represent optimal starting materials for extrusion) hasestablished that zeolite preforms that are sufficiently mechanicallystable, crack-free, compact and binder-free can be produced via thesolidification as well as the conversion of zeolite precursor componentsinto zeolite for the applications mentioned above, wherein thedisadvantages of known products described in the prior art are notobserved.

Surprisingly, it has further been found that mechanically stable,crack-free, compact and binder-free zeolite preforms can be obtainedwith the aid of the pressing and casting shaping methods in thetechnology chain, after converting the used zeolite precursor intozeolite.

Another aspect of the present invention relates to the use of thecompact zeolite preforms described above as adsorbent agents, e.g. forprocessing gas in technical adsorption processes. Further preferredapplications of the preforms in accordance with the invention relate tomethods for thermal-chemical energy storage, such as heat pumps or forgenerating cold temperatures, as a catalyst or catalyst component or asa carrier for zeolite membranes.

An x-ray graph of the compact zeolite preforms in accordance with theinvention indicate a zeolite fraction of between 86 and 100%. As theequilibrium adsorption capacities are only slightly below those of theinitial zeolite powder that is used, it can be assumed that the compactzeolite preforms consist of approx. 100% zeolite, but as has alreadydescribed in²³, part of this zeolite is not detectable by X-ray.Obviously similar phenomena occur in both methods, despite differentproduction methods.

Through the production method that has been explained, the goal ofproducing compact zeolite preforms that have a high space filling indexusing active zeolite material has been achieved. The various ceramicmoulding technologies shape the production process flexibly, so that itis possible to produce the exact preform geometry that seems to be mostadvantageous for the later application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows diffraction patterns of a zeolite 4A powder (broken line,initial material 1) and a produced compact zeolite preforms.

FIG. 2 shows diffraction patterns of a zeolite X powder and a zeolite 7channel tube which is produced with a faujasite structure and a zeoliteX composition.

FIG. 3 shows diffraction patterns of zeolite Y powder and a zeolite 1channel tube which is produced with a faujasite structure and a zeoliteY composition.

DETAILED DESCRIPTION

The following examples aim to illustrate the principles of the presentinvention in greater detail, however they do not restrict the scope ofprotection in any way.

Initial Material 1: Zeolite 4A

For the examples described here, zeolite 4A (Zeolon, MAL AG) with thefollowing properties has been used for the production of compactbinder-free zeolite 4A preforms:

Water absorption capacity 24.8% d₅₀ (average particle diameter) 3.7 μmLoss on ignition 20.0%Particle diameter: “Mastersizer 2000” and dispersing instrument “Hydro2000 S” from Malvern InstrumentsLoss on ignition: Loss of mass after 1 h at 950° C.

Initial Material 2: Zeolite X

For the examples described here, zeolite X (KÖSTROLITH® NaMSX,Chemiewerk Bad Köstritz GmbH) with the following properties has beenused for the production of compact binder-free zeolite X preforms:

Modulus (RFA) 2.34 Water absorption capacity 30.8% d₅₀ 3.6 μm Loss onignition 21.1%

Module: X-ray fluorescence spectrometer “S4 EXPLORER” from Bruker-AXSGmbH, Karlsruhe, software package “SPECplus”

Initial Material 3: Zeolite Y

For the examples described here, zeolite Y (CBV100, ZeolystInternational) with the following properties has been used for theproduction of compact binder-free zeolite Y preforms:

Modulus (RFA) 5.3 Water absorption capacity 29.1% d₅₀ 4.5 μm Loss onignition 25.2%

Initial Material 3: Kaolin

The commercially available Kaolin KF-2 that was used (Prosco Ressources)has the following properties:

Si0₂/wt. % 53.1 Al₂0₃/wt. % 44.1 Quartz content/% 2

SiQ₂, Al₂O₃ content: X-ray fluorescence spectrometer “S4 EXPLORER” fromBruker-AXS GmbH, Karlsruhe, software package “SPECplus”

Quartz content: X-ray powder diffractometer (XRD) “D4 ENDEAVOR” fromBruker-AXS GmbH, Karlsruhe, software package “DIFFRACplus”

Conventional Honeycombs Containing Binder from Zeolite Type 4A

For comparison, a continuous honeycomb strand is produced by extrusionwith a vacuum screw extruder from a plastic mass produced in a twinshaft mixer consisting of 78 wt. % zeolite 4A, 18 wt. % bentonite(Cerartosil; inorganic binder), 2 wt. % organic component with atemporary binder effect (Tylose CER 40600) and 2 wt. % glycerol andwater. For the subsequent drying, the strand is cut into 300 mm longhoneycomb pieces and dried at 60° C. After drying, the honeycombs arecut into pieces (9 cm long) and subsequently thermal treated at 600° C.In this temperature treatment, the organic matter and water are removedand the structure of the honeycomb is solidified by the inorganicbinder.

Comparison Material 1: Zeolite 3A Powder

The commercially available zeolite 3A powder (Luoyang Jianlong ChemicalIndustrial Co., LTD.) has the following properties:

Ion exchange level/% Water adsorption capacity/% 58 25.7Ion exchange level: X-ray fluorescence spectrometer “S4 EXPLORER” fromBruker-AXS GmbH, Karlsruhe, software package “SPECplus”

Comparison Material 2: (Zeolite 5A Powder)

The Zeolite 5A powder (Chemiewerk Bad Köstritz GmbH) has the followingproperties:

Ion exchange level/% Water adsorption capacity/% 74 22.8

All of the analytical tests carried out showed that the preforms arehomogeneous, both after the conversion of the zeolite precursorcomponent into zeolite and after the ion exchange.

Example 1

Starting with 2250 g of zeolite 4A powder (initial material 1) and 990 gof kaolin (initial material 4) a plastic mass is produced in a twinshaft mixer using 5 wt. % of the organic component with a temporarybinder effect MHPC 20000, 2% glycerol and water. The plasticized mass isshaped in a vacuum screw extruder. At the same time, the mass isdeaerated in the vacuum chamber of the extruder and by means of apressing screw, it is pressed through a shaping die to form a honeycombshape. The honeycomb that is formed emerges as a compact continuouspreform. After extrusion, it is cut to a length of 100 mm suitable forthe subsequent technological steps, dried with a 5% loss on drying andthen annealed at 550° C. on firing auxiliaries.

Using diamond separation blades, the compact, tempered honeycombs arecut dry to 9 cm in length.

After tempering, the non-zeolite components of the honeycomb areconverted into zeolite with the Linde type A structure. For this,honeycombs with a total weight of 50 g are rinsed with 300 ml ofdeionized water, i.e. left in water for 30 mins. After the predeterminedtime, the water is poured off as much as possible and replaced with thereaction solution. This consists of 500 ml of deionized water, 38 g of a50% sodium hydroxide solution and 8.5 g of sodium aluminate (20% Na₂O,20% Al₂O₃). The honeycombs are aged in this solution for 1 h at roomtemperature and then heated to 85° C. and kept at this temperature for16 h.

After the reaction time, the material is cooled, and the supernatantsolution is removed by decantation. The honeycombs are washed threetimes with 200 ml of deionized water and filtered as dry as possibleusing a vacuum via a Buchner funnel. They are then dried completelyunder an IR lamp and finally activated at 450° C. within 2 h.

The material produced in this way indicates a crystallinity of 92% (XRD)based on the initial zeolite powder and a static water absorptioncapacity of 24.7%. The zeolite content determined by the wateradsorption is 99.6%.

The material produced in this way has a residual moisture content of 0.8(mass) % (determined by Karl Fischer titration (700° C.)).

The following table shows a comparison between the initial zeolitepowder, the clay bonded zeolite honeycombs and the binder-free zeolitehoneycombs with a Linde type A structure.

TABLE 2 C Zeolite 4A powder, clay bonded and binder-free zeolite 4A.Zeolite Clay-bonded zeolite Binder-free 4A powder 4A honeycomb honeycomb(initial (conventional (zeolite 4A, material 1) compact preform)example 1) Crystallinity (water 100 79.8 99.6 adsorption capacity; basedon the zeolite 4A initial powder)/% Crystallinity (XRD 100 78 92 basedon the zeolite 4A initial powder)/% Modulus 2.00 — 2.00 Water adsorption24.8 19.8 24.7 capacity/mass % Average pore diameter — 0.30 0.48 of thePore transporta- tion system - μm Static CO₂ adsorption capacity at 25°C./ cm³/g at 1.8 Torr 31.3 19.2 30.1 at 34 Torr 66.4 47.5 65.6 at 250Torr 84.7 63.0 82.2 Static N2 adsorption 8.4 6.5 8.9 capacity at 30° C.,750 mbar/cm³/gCrystallinity (XRD): X-ray powder diffractometer (XRD) “D4 ENDEAVOR”from Bruker-AXS GmbH, Karlsruhe, software package “DIFFRACplus”

Water adsorption capacity: The material is activated for 2 h at 450° C.and charged with water at 55% relative humidity and 25° C. untilequilibrium is reached.

Average pore diameter: Hg porosimeter PASCAL P140, -P440 from Porotec.Static CO₂ and N₂ adsorption capacity: The material is activated for 2 hunder 0.01 mbar at 400° C. The measurement takes place at 25° C. on asorption “GEMINI” instrument from Micromeritics.

FIG. 1 shows the diffraction patterns of zeolite 4A powder (broken line,initial material 1) and the produced compact zeolite preforms (solidline, example 1) are shown. These are nearly identical.

Example 2

48 g of the type 4A binder-free zeolite honeycombs in accordance withexample 1 (in accordance with the invention) are stored in water for 1 hat room temperature and then for 48 h at room temperature in a 5%solution of potassium chloride (1 litre). Occasionally, the supernatantsolution is rotated. Subsequently, the solution is decanted and thehoneycombs are washed and dried. The resulting compact zeolite preforms3A exhibit the following features:

Comparison material 1 Binder-free honeycomb (zeolite 3A powder) (zeolite3A, example 2) Ion exchange level/% 58 63.5 Water adsorption 25.7 22.6capacity/%

Example 3

48 g of the type 4A binder-free zeolite honeycombs in accordance withexample 1 (in accordance with the invention) are stored in water for 1 hat room temperature and then for 48 h at room temperature in a 5%solution of calcium chloride (1 litre). Occasionally, the supernatantsolution is rotated. Subsequently, the solution is decanted and thehoneycombs are washed and dried. The resulting compact zeolite preforms5A exhibit the following features:

Comparison material 1 Binder-free honeycomb (zeolite 5A powder) (zeolite5A, example 3) Ion exchange level/% 74 76 Water adsorption 22.8 22.7capacity/%

Example 4

Starting from 1.7 kg of zeolite X powder (initial material 2), 850 g ofkaolin (initial material 4) and 25 g of a sodium hydroxide solution(50%) a plastic mass is produced in a twin-shaft mixer using 5% of theorganic component with a temporary binder effect MHPC 20000, 2%glycerol, lubricant and water. The shaping of the plasticized mass takesplace in a vacuum screw extruder. The mass is vented in the vacuumchamber of the extruder and by means of a press screw, it is pressedthrough a 7 channel forming tube tool. The 7 channel tube is formed as acompact continuous preform. After extrusion, it is cut to a length of500 mm suitable for the subsequent technological steps, dried with a 5%loss on drying and then annealed at 550° C. on firing auxiliaries:

Using diamond separation blades, the annealed 7-channel tubes are cutdry to 100 mm in length.

After tempering, the non-zeolite components of the 7-channel tubes areconverted into zeolite with a faujasite structure. For this, 7-channeltubes with a total weight of 30 g are watered with 200 ml of deionizedwater, i.e. left in water for 60 mins. After the predetermined time, thewater is largely decanted and replaced by and the reaction solution.This consists of 240 ml of deionized water, 54 g of a 50% sodiumhydroxide solution and 15 g of sodium silicate (8% Na₂O, 27% SiO₂). Thewatered 7-channel tubes are aged in this solution for 2 hours at roomtemperature, then heated to 85° C. and kept at this temperature for 16h.

After the reaction time the material is cooled down and the supernatantsolution is removed by decantation. The 7-channel tubes are washed threetimes with 200 ml of deionized water, filtered as dry as possible usinga vacuum via a Buchner funnel and then dried completely under an IRlamp.

The material produced in this manner exhibits a crystallinity of 90%(XRD) based on the initial zeolite powder and a static water absorptioncapacity of 29.2%. The zeolite content determined by the wateradsorption is 94.8%.

The following table shows a comparison between the initial zeolitepowder and the compact binder-free zeolite preforms with a faujasitestructure.

TABLE 3 Comparison between zeolite powder and binder-free zeolite 7channel tubes with a faujasite structure Zeolite Binder-free compact Xpowder preforms of the faujasite (initial structure and zeolite Xmaterial 2) composition (example 4) Crystallinity (water adsorption 10094.8 capacity; based on the zeolite 4A initial powder)/% Crystallinity(XRD based on 100 90 the zeolite X initial powder)/% Modulus 2.34 2.35Water adsorption capacity/mass % 30.8 29.2 Average pore diameter of the— 0.89 pore transportation system/μm Static CO₂ adsorption capacity at25° C./cm³/g at 1.8 Torr 35.0 28.9 at 34 Torr 81.7 74.8 at 250 Torr120.7 112.1 Static N₂ adsorption 10.7 9.8 capacity at 30° C., 750mbar/cm³/g Micropore volumes/cm³ g 0.33 0.31

FIG. 2 shows the diffraction patterns of zeolite X powder (dotted line,initial material 2) and the zeolite 7 channel tube which is producedwith a faujasite structure and a zeolite X composition (solid line,example 4). These are nearly identical.

Example 5

Starting from 2.5 kg of zeolite X powder (initial material 3), 850 g ofkaolin (initial material 4) and 80 g of sodium hydroxide solution (50%)a plastic mass is produced in a twin-shaft mixer using 5% of the organiccomponent with a temporary binder effect MHPC 20000, 2% glycerol,lubricant and water. The shaping of the plasticized mass takes place ina vacuum screw extruder. The mass is vented in the vacuum chamber of theextruder and by means of a press screw, it is pressed through a 1channel forming tube tool. The 1 channel tube is formed as a continuousstrand. After extrusion, it is cut to a length of 500 mm suitable forthe subsequent technological steps, dried with a 5% loss on drying andthen annealed at 550° C. on firing auxiliaries:

Using diamond separation blades, the annealed 1 channel tubes are cutdry to 200 mm in length.

After tempering, the non-zeolite components of the 1 channel tubes areconverted into zeolite with a faujasite structure. For this, 1 channeltubes with a total weight of 30 g are watered with 200 ml of sodiumhydroxide solution (1%), i.e. left in a sodium hydroxide solution (1%)for 60 mins. After the predetermined time, the sodium hydroxide solutionis largely decanted and replaced by and the reaction solution. Thisconsists of 190 ml of deionized water, 8 g of a 50% sodium hydroxidesolution and 60 g of sodium silicate (8% Na₂O, 27% SiO₂). The watered 1channel tubes are aged in this solution for 2 hours at room temperature,then heated to 90° C. and kept at this temperature for 20 h.

After the reaction time, the material is cooled, and the supernatantsolution is removed by decantation. The 1 channel tubes are washed threetimes with 150 ml of a sodium hydroxide solution (1%) and filtered asdry as possible using a vacuum via a Buchner funnel. They are then driedcompletely under an IR lamp.

The material produced in this manner exhibits a crystallinity of 96%(XRD) based on the initial zeolite powder and a static water absorptioncapacity of 28%. The zeolite content determined by the water adsorptionis 96.2%.

The following table shows a comparison between the initial zeolitepowder and the binder-free 1 channel tubes with a faujasite structureand zeolite Y composition.

TABLE 4 Comparison between zeolite powder and binder-free zeolite 1channel tubes with a faujasite structure. and zeolite Y compositionZeolite Y Binder-free compact powder - preforms of the faujasite(initial structure and zeolite Y material 3) composition (example 5)Crystallinity (water adsorption 100 96.2 capacity; based on the zeoliteY initial powder)/% Crystallinity (XRD based on 100 96 the zeolite Yinitial powder)/% Modulus 5.3 5.3 Water adsorption capacity/mass % 29.128.0 Average pore diameter of the — 0.30 pore transportation system/μmStatic CO₂ adsorption capacity at 25° C./cm³/g at 1.8 Torr 3.9 4.4 at 34Torr 32.2 31.4 at 250 Torr 94.8 90.8 Static N₂ adsorption 5.5 5.4capacity at 30° C., 750 mbar/cm³/g Micropore volumes/cm³ g 0.33 0.32

FIG. 3 shows the diffraction patterns of zeolite Y powder (dotted line,initial material 3) and the zeolite 1 channel tube which is producedwith a faujasite structure and a zeolite Y composition (solid line,example 5). These are nearly identical.

Example 6

The production of 1 channel tubes takes place in the same way as example5.

After tempering, the non-zeolite components of the 1 channel tubes areconverted into zeolite with a faujasite structure. For this, 1 channeltubes with a total weight of 30 g are moved with a reaction solutionconsisting of 190 ml deionized water, 8 g of a 50% sodium hydroxidesolution and 60 g of sodium silicate (8% Na₂O, 27% SiO₂) and then heatedto 90° C. and kept at this temperature for 20 h.

After the reaction time, the material is cooled, and the supernatantsolution is removed by decantation. The 1 channel tubes are washed threetimes, each time with 200 ml of deionized watered and filtered as dry aspossible using a vacuum via a Buchner funnel. They are then driedcompletely under an IR lamp.

The material produced in this manner exhibits a crystallinity of 81%(XRD) based on the initial zeolite powder, a modulus of 5.3% and astatic water absorption capacity of 26.9%. The zeolite contentdetermined by the water adsorption is 92.4%.

Example 7

The production of 1 channel tubes takes place in the same way as example5.

After tempering, the non-zeolite components are converted into zeolitewith a faujasite structure. For this, 1 channel tubes with a totalweight of 30 g are moved with a solution consisting of 190 ml deionizedwater, 8 g of a 50% sodium hydroxide solution and 60 g of sodiumsilicate (8% Na₂O, 27% SiO₂) and the mixture is aged for 2 h at roomtemperature. Then, they are heated to 90° C. and kept at thistemperature for 20 h.

After the reaction time, the material is cooled, and the supernatantsolution is removed by decantation. The 1 channel tubes are washed threetimes, each time with 200 ml of deionized watered and filtered as dry aspossible using a vacuum via a Buchner funnel. They are then driedcompletely under an IR lamp.

The material produced in this manner exhibits a crystallinity of 84%(XRD) based on the initial zeolite powder, a modulus of 5.3% and astatic water absorption capacity of 27.5%. The zeolite contentdetermined by the water adsorption is 94.5%.

Example 8

A moist mixture is produced in a mixer at 1000 rev./min from zeolitewith a Linde type A structure (initial material 1), kaolin (initialmaterial 4) and a sodium hydroxide solution at 30 parts kaolin (by mass)(dry) to 70 parts 4A zeolite (by mass) (dry) to 3.5 parts of a 50% NaOHsolution (by mass). 2% (10%) Mowiol binder solution is added in drops.The mixture is stored in a covered state for 24 hours in order tohomogenize the humidity. The mixture is then ground through a sieve witha mesh width of 1 mm and the sieve granules obtained in this way aredried with a 6% loss on drying. After drying, the granules arepre-pressed on a dry press with a press pressure of 600 MPa to thecylinders with a diameter of 18 mm and a thickness of 10 mm. By grindingthe compacts through a 1 mm sieve, it is possible to obtain pressablegranules. From these granules, preforms with a diameter of 60 mm and athickness of 3 mm are then produced on the dry press with a specificpressure of 1000 MPa. Annealing of these discs takes place when they areplaced on firing plates made from engobed silicon carbide at 500° C.

After tempering, the non-zeolite components of the preforms areconverted into zeolite with Linde type A structure in the same way as inexample 1.

TABLE 5 Properties of the binder-free zeolite 4A discs. Zeolite 4ABinder-free disc powder (initial (zeolite 4A, material 1) example 8)Crystallinity (XRD based on the 100 92 zeolite 4A initial powder)/%Crystallinity (water adsorption 100 98.8 capacity based on the zeolite4A initial powder)/% Modulus 2.00 2.01 Water adsorption capacity/Mass %24.8 24.5 Average pore diameter of the — 0.71 pore transportationsystem/μm

Example 9

In a 10 l grinding drum, 4 kg grinding balls (20 mm) are initiallyweighed. 4 kg of raw material mixture is them added consisting of 70parts (by mass) of zeolite 4A powder (dry) and 30 parts (by mass) ofkaolin (dry). After adding 4 l deionized water and 0.3% dispersant(Dolapix CE64) the grinding drum is closed and the slip is ground to agrinding frame for 24 h. After the grinding process, the slip is pouredthrough a 0.1 mm sieve. The casting of the slip is carried out as aplate measuring 100×100×12 mm³ in dry plaster cast. After standing forapprox. 75 minutes (depending on shard formation, which in turn affectedby the ambient temperature and humidity) the plate is removed from themould and dried with drying loss of 5%). Annealing of these plates takesplace when they are placed on firing plates made from engobed siliconcarbide at 500° C.

After tempering, the non-zeolite components of the preforms areconverted into zeolite with Linde type A structure in the same way as inexample 1.

TABLE 6 Properties of the binder-free zeolite 4A plate. Zeolite 4ABinder-free disc powder (initial (zeolite 4A, material 1) example 8)Crystallinity (XRD based on 100 92 the zeolite A initial powder)/%Crystallinity (water adsorption 100 98.8 capacity based on the zeolite4A initial powder)/% Modulus 2.00 20.01 Water adsorption capacity/Mass %24.8 24.5

LITERATURE

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1. A Compact zeolite preform, characterized in that the preform has azeolite content of at least 90 percent.
 2. The Compact zeolite preformin accordance with claim 1, characterized in that the preform is basedon one of zeolite Y zeolite X, and zeolite A.
 3. The Compact zeolitepreform in accordance with claim 1, characterized in that the preform isin the form of one of a plate, a tube, a solid cylinder, and a honeycombstructure.
 4. A method for producing a compact zeolite preform, themethod comprising: a) processing a mouldable mixture, comprisingzeolite, and a zeolite precursor component, into the preform, b)thermally treating the preform; and c) aging and bringing the preforminto contact with a further component from which, in combination withthe zeolite precursor component, zeolite can be produced and exposed toconditions under which the zeolite forms from the further component andthe zeolite precursor component.
 5. The method in accordance with claim4, further comprising shaping the mouldable mixture by one of extruding,pressing and casting
 6. The method in accordance with claims claim 4,characterized in that kaolin is used as the zeolite precursor component.7. The method in accordance with claims claim 4, characterized in thatthe zeolite and the zeolite precursor component in step a) are in aweight ratio of 10:1 to 1:10.
 8. The method in accordance with claim 4,characterized in that the thermally treating takes place at atemperature of 550° C. to 850° C.
 9. The method in accordance with claim4, characterized in that the aging and bringing follows the thermallytreating.
 10. The method in accordance with claim 4, characterized inthat a sodium silicate solution and/or a sodium aluminate is used as thefurther component in step c).
 11. The method in accordance with claim 4,characterized in that during the aging and bringing the furthercomponent and the zeolite precursor component are brought into contactat a temperature in the range of 75° C. to 100° C.
 12. The method inaccordance with claim 11, characterized in that during the aging andbringing the further component and the zeolite precursor component arebrought into contact over a period of 1 to 48 hours.
 13. The method inaccordance with claim 11, characterized in that the bringing is carriedout at temperatures between 75° C. to 100° C. and wherein the aging iscarried out at a temperature of 15 to 60° C. over a period of 0.5 to 24hours.
 14. The method in accordance with claim 4, further comprisingwashing the preform, the further component, and the zeolite precursorcomponent with one or more alkali hydroxide solutions and water, driedand activated up to a residual moisture content of <2 wt. %.
 15. ACompact zeolite preform according to the method specified in claim 4.16. (canceled)
 17. The method of claim 4, further comprising wateringthe preform.
 18. The Compact zeolite preforms of claim 1, wherein thepreform has a zeolite content of at least 95%.
 19. The method inaccordance with claim 7, characterized in that the zeolite and thezeolite precursor component in step a) are in a weight ratio of 1:1 to6:1.
 20. The method in accordance with claim 8, characterized in thatthe thermally treating takes place at a temperature of 550 to 650° C.21. The method in accordance with claim 11, characterized in that duringthe bringing the further component and the zeolite precursor componentare brought into contact at a temperature in the range of 80° C. to 95°C.